The document discusses several TCP/IP protocols used for communication over the internet including SMTP, HTTP, FTP, TFTP, NNTP, SNMP, POP, IMAP, and Telnet. It describes the basic functions and workflows of each protocol.

1. TCP/IP Services and Applications

2. Simple Mail Transfer Protocol (SMTP)
• Specifies how mail should be delivered from one system
to another
• Standard protocol used for transferring email from one
computer to another
• Makes connection between sender’s server and recipient
and then transfer messages
• For sending mails SMTP server must supply name of the
destination host as well as name of destination mailbox

3. SMTP Work Flow
• A two-way transmission channel established between the sender
SMTP and a receiver SMTP
• Commands are generated by sender SMTP and sent to receiver SMTP

4. Hypertext Transfer Protocol (HTTP)
• Set of rules used to exchange files on World Wide Web
• Users can exchange text, graphic images, sound, video
and other multimedia files
• Defines how messages are formatted and transmitted
over the Internet

5. HTTP Work Flow
• HTTP works on request and
response between browser
and server
• Web server is designated
to handle HTTP requests
then sends requested
HTML page
 Data is carried in the Multipurpose Internet Mail
Extensions (MIME) format between the request
and response

6. Uniform Resource Locator (URL)
• Text string that is used to locate a file or an object on an
internet
• URL Syntax
<scheme>:<scheme-specific-part>
• E.g. http:// www.microsoft.com “http” is the scheme
and “www.microsoft.com” is the scheme specific part

7. File Transfer Protocol (FTP) and
show configuration from CBT
• Used over Internet to exchange files
• Uses Internet's TCP/IP protocols to enable data transfer
• Establishes two way connections between computers
one for transferring data and other for sending control
information

8. FTP Communication
• Machine that are involved in an FTP transaction – Client (local
host) machine and a server (remote host)
• Client machine initiates transfer
• Get command used to
copy files from server to
client
• Put command is used to
upload files from client to server
The control connection is established when the user starts an
FTP session
If there are many files to be transmitted the data connection can
be opened and closed multiple times

9. Trivial File Transfer Protocol (TFTP) - I
• Used to transfer files to and from a remote computer
• Used by servers to boot diskless workstations, X-
terminals and routers
• Start with a small amount of built-in software

10. Trivial File Transfer Protocol (TFTP) – II
• Connection and Communication between Client/Server
– Communication and messaging different (send data byte
by byte) in TFTP when compared with FTP
– TFTP uses UDP (port no. 69)
– Process of transferring a file:
• Initial Connection
• Data Transfer
• Connection Termination
Multiple TFTP exchanges are possible simultaneously by
a server using unique port number

11. Network News Transfer Protocol (NNTP)
• Used to transfer Usenet news from one machine to
another machine
• Usenet news is a large collection of discussion groups,
covering a wide range of topics
• NNTP provides connection-oriented service
• Communication takes place between a client and a
server that keeps netnews on both the places

12. Simple Network Management Protocol
(SNMP)
• Framework for managing devices over Internet using
TCP/IP protocol suite
• Provides set of fundamental operation for monitoring
and maintaining devices in the network
• Agent is server process that maintains Management
Information Base (MIB) database for host
• Based upon client-server model

13. SNMP Management Components
• SNMP uses two protocols to manage tasks:
– Structure of management Information (SMI) – defines
rules for naming an object and defining the type of object
– Management Information Base (MIB) – defines the
number of objects
• Components of network management on the Internet:
– SNMP
– SMI
– MIB

14. Security
• SNMP leads to vulnerability to a variety of security threats
because of lack of any authentication capabilities
Threats
Modification Message
Masquerading Disclosure
of Information Sequence

15. Post Office Protocol (POP)
• Used to retrieve email from remote server to local client
over TCP/IP connection
• E-mail clients using POP3 connect, retrieve all messages or
store them on user's PC as new messages or delete them
from server and disconnect
• POP3 is a TCP/IP client/server protocol
• Session States:
– Authorization State
– Transaction State
– Update State

16. POP Session states

17. Internet Message Access Protocol (IMAP)
• Enables the users to work with the mail on the server
• Does not download the mails
• Used to access e-mails from a local server
• Working with mails
– Accessing and deleting mails
– Attachments

18. IMAP Advantages and Disadvantages
• Advantages:  Disadvantages:
– As the e-mail folders are  Complicated
stored on the server, the
user is able to read email  Results in higher server
from any computer loads than POP3
which belongs to the  Utilizes a lot of server
network resources
– To access more than one
account from different
locations, IMAP will be
the most efficiently

19. Electronic Mail (E-mail)
• Provides way to communicate and send letters over the
Internet
Mail
Delivery
System
Mail Mail Mail Mail
User Submission Transfer Delivery
Agent (MUA) Agent (MSA) Agent (MTA) Agent (MDA)

20. E-mail Architecture
• An E-mail system is divided into two sub-systems:
– User Agents (UA)
– Message Transfer Agent (MTA)
• E-mail architecture supports basic functions:
– Composition
– Transfer
– Reporting
– Displaying
– Disposition

21. User Agent (UA)
• Allows user to send and read e-mail
• Program that provide various methods such as command
based, menu based or graphical to interact with the e-
mail
• Sending Mail - User needs to provide message,
destination address and other parameters while sending
an e-mail
• Receiving Mail - The UA at the recipient end checks the
mailbox periodically for new e-mail

22. Message Transfer Agent (MTA)
• Moves message from source to destination
• Process that run in the background and transfers the e-
mail through system
• Message Format
– RFC 822 – Specifies syntax for text messages within the
framework of electronic mail
– Two components – Envelope and Content
• MIME – Multi purpose Internet Mail Extension
• Header fields defined in MIME – Version, Content Type,
Content-transfer-encoding, content ID and description

23. RFC 822 Message Formats
Header Meaning
To: Primary recipient e-mail address
Cc: Secondary recipient e-mail address
Bcc: Blind carbon copy e-mail address
From: User who created the message
Sender: Senders e-mail address
Received: Line added by each transfer agent along the route
Return-Path: Can be used to identify a path back to the sender
Date: The date and time of the message sent
Reply-To: Email address to which replies should be sent
Message-Id: Unique number for later reference
In-reply-To: Identification of the message to which this is a reply
References: Over relevant message-id
Keywords: Keywords chosen by user
Subject: Summary of the message

24. E-mail Privacy
• Protection of e-mail from unauthorized access and
inspection
• Connection to the Internet should be secured to provide
privacy between routers and other connections between
them
• Data encryption provides privacy by translating the
content into different format which is unreadable

25. BOOTP and DHCP - I
• BOOTP – First automated configuration tool for IP hosts
– Bootstrapping – Provides the host with the
capability of getting IP addresses while machine
boots
– Requires two phases:
• Client provided with address and other parameters
• Client downloads softwares to function on network and
perform tasks

26. BOOTP and DHCP – II
• Dynamic Host Configuration Protocol (DHCP) – Successor
of BOOTP with different features
• Dynamically assign addresses to clients and centrally
manage
• Consists of two major components – 1. Address
allocation mechanism 2. Protocol that allows clients and
server to communicate
• DHCP standard includes three different address
allocation mechanisms:
– Manual , Automatic and Dynamic

27. Difference between BOOTP and DHCP
Bootstrap Protocol (BOOTP) Dynamic host configuration protocol (DHCP)
Fails if host moves from one physical network to another Provides with temporary IP address on request, hence works
efficiently when host moves from one physical network to
another
Cannot provide host with temporary IP address Provides host with temporary IP address
This type of IP address configuration is designed to This type of configuration is used to configure IP addresses to
configure hosts, which are diskless workstation. computers or host that are frequently relocating from
network to network
Supports finite or limited number of client IP address Supports large and extensible number of client IP address
configuration parameters configuration parameters as compared to BOOTP

28. TELNET
• Network protocol used on internet or local area network
connections
• Terminal emulation program for TCP/IP networks
• Enables to control server and communicate with other
servers on network

29. Working of TELNET
• Telnet client – Software that acts as interface to user,
processing user commands and presenting output from
remote machine
• Telnet server - Program running on remote computer
that has been set up to allow remote session
• Telnet runs over connection-oriented TCP
• TCP connection maintained for duration of Telnet
session
• Client and server send information at same time over
Telnet session because TCP is a full-duplex

30. World Wide Web (WWW) - I
• WWW is a network of Internet servers, which support
documents that are developed using HTML
• Hyper Text Markup Language (HTML) is a language in
which these documents are formatted
• Client-side
– Computer application – Web browser that runs on user’s
local computer and connects to server
– Interpreter that interprets code in an HTML page
– Operations carried out on client-side

31. World Wide Web (WWW) – II
• Server Side
– Software program – Web server that runs on a remote
server
– Manages and shares web based applications
– Operations include processing and storage of data from
client to server

32. Hyper Text Markup Language (HTML)
• Markup language used to create web pages with
hypertext and other information to be displayed on web
browser
• A Web page consists of HTML tags which are also called
as standalone and container tags
• Tag starts with an open angular bracket and word and
then closing angular brackets

33. Java
• Programming language with number of features
• Developed by Sun Microsystems
• Applet
– A program written in Java programming language
– Features - Display document, send message to other
applets, play music, display images and videos
• Servlets
– Program that runs in response to client connection to
server
– Program which run on a web server and handles user
requests and generates response

34. Working on WWW
• Structure of finding information over internet divided
into three stages:
– Finding documents
– Formulating queries
– Determining relevance